Method of extracting lutein/xanthophylls from natural materials and highly purified lutein/xanthophylls obtained from the method thereof

ABSTRACT

The present invention provides the new method for extracting lutein from natural materials wherein the said method comprises of modification of natural lutein ester in the natural materials to free lutein and/or low molecular weight lutein ester, extraction of the said natural materials with supercritical fluid at the optimal conditions. The said method yields high amount of crude lutein with high purity due to the mild condition used for extraction. Therefore, no degradation of the desired product is occurred. The crude lutein can be further purified with chromatography in order to obtain the highly purified lutein. The method according to this invention can be applied to the extraction of xanthophylls or others beside lutein.

FIELD OF THE INVENTION

Organic chemistry related to the extraction of lutein/xanthophylls especially the extraction of lutein from marigold flowers with supercritical fluid and highly purified lutein/xanthophylls obtained from the method thereof.

BACKGROUND OF THE INVENTION

Marigold (Tagetes erecta) is an annual flowering plant having wide range of colors with the tube-like petals. In Thailand, marigolds are cultivated mainly in Suphanburi, Kanchanaburi, Lampoon and Chiang Mai provinces. Due to the high content of caroteniods, marigolds are commonly used in animal feeds for the animals' health benefits: Moreover, the brightly yellow and red colors of carotenoids in marigold are also used as natural colorants in feeds i.e. for chicken feed which yields egg yolk with bright red color.

The major carotenoids in marigold is xanthophylls (up to 1%), especially lutein.

Lutein is xanthophyll which exhibits antioxidative property and also the composition of retina in the eye. It has been reported that lutein can be used effectively for the treatment of diseases related to vision and also used for maintaining functions in human body. Therefore, the method of extracting lutein from natural materials is of the interest.

One of the attempts is to extract lutein from marigold by organic solvent especially non-polar solvent such as hexane. The material contained in the organic solvent is called miscellar. To obtain lutein product, the remaining solvent must be evaporated. The crude extract obtained after solvent evaporation is called oleoresin. The oleoresin contains 10% (w/w) xanthophylls which lutein is the major product.

One of the problems is that the strictly requirement of absolute removal of the extraction solvent. The remaining solvent must not exceed the international standard. This is due to the fact that remaining solvent may cause the serious health problem to consumers.

There has been an attempt to extract lutein by using alternative solvent i.e. supercritical fluid especially supercritical carbon dioxide which is safer to use for consumer products. Moreover, supercritical carbon dioxide possesses high diffusivity and low viscosity when compared to liquid solvents. Supercritical carbon dioxide is, therefore, suitable for extraction due to its mass transfer property. Moreover, it can be used for the extraction at low temperature (critical temperature is 30° C.) which prevent the decomposition or degradation of the extracted materials. It can also be removed easily by pressure reduction or temperature reduction.

U.S. patent No. 20040267033 described the extraction of lutein from marigold by supercritical carbon dioxide at 70° C. and 475 bar, gaining 85-90% yield. The problem of this invention is that the higher temperature must be used in order to obtain the xanthophyll with higher purity which is required for the application in nutraceuticals or drugs. The problem associated with increasing temperature during the extraction is the degradation or decomposition of xanthophylls whereas the increase in pressure also consumes more energy and posts more risks. Therefore, the supercritical fluid cannot be practically used for the industrial extraction of xanthophylls especially highly purified lutein. The method according to the above invention still has problem with the strong conditions even though- it can solve the safety problem of liquid solvents.

Other related documents include U.S. Pat. Nos. 44,669,223, 5,120,558, 5,932,101, 6,737,552, 6,350,890, 7,214,379, 5,780,693, 6,262,284, 7,351,424, and 6,689,400.

This inventor had studied the problems in prior arts and the natural properties of this compound and other xanthophylls in nature. It was found that lutein and other xanthophylls in nature are mostly in the forms of diester with fatty acid i.e. lutein dipalmitate, lutein dimyristate, zeaxanthine dipalmitate and zeaxanthine dimyristate. These diesters have high molecular weights i.e. lutein dipalmitate has molecular weight at 1045 Dalton whereas free lutein has molecular weight at only 569 Dalton. Consequently, the extraction of natural lutein/xanthophylls in this complex forming molecule with supercritical fluid would therefore require high temperature and/or high pressure to obtain the yield of lutein/xanthophylls similar to the solvent extraction method.

This inventor performed the extraction of lutein from natural materials directly with supercritical fluid at reduced temperature 60° C. and varied the condition of pressure at 300, 350 and 400 bar, respectively for 4 hours as shown in FIG. 1.

FIG. 1 shows the yield of crude lutein obtained from extraction. Although the crude lutein increased by increasing the pressure, the maximum yield is only 74.40% at 400 bar.

Moreover, this inventor applied the crude lutein to chromatography purification; it was found that the free lutein was mixed with the very high amount of lutein ester as shown in FIG. 2.

Until now, there is no report of extraction of crude natural lutein with supercritical fluid at low temperature and pressure with the product yield higher than 90%.

Therefore, this inventor aimed to modify lutein ester/xanthophylls ester to free lutien/xanthophylls and/or low molecular weight lutein ester/xanthophyll esters before extraction with supercritical fluids. The natural materials containing lutein/xanthophylls include marigold, kale, spinach, microbial cells i.e. bacteria, yeasts, fungi and microalgae and algae. This invention allows the extraction of crude lutein from natural materials with supercritical fluids at low temperature and pressure but still provides higher yield.

SUMMARY OF THE INVENTION

The present invention provides the new method for extracting lutein from natural materials which yield higher crude lutein and/or higher purified lutein than previously existed.

Another objective of this invention is to provide the extraction method which is applicable to xanthophylls which are in the same group of compound as lutein.

Another objective of this invention is to provide highly purified lutein/xanthophylls obtained from the methods according to the present invention.

The method according to this invention includes the modification of natural lutein ester in the natural materials to free lutein and/or low molecular weight lutein ester, extraction of the said natural materials with super-critical fluid at the optimal conditions. The method according to this invention is capable of lutein extraction from natural materials in high amount because the efficiency of extraction is improved. The crude lutein can be further purified with chromatography in order to obtain the highly purified lutein.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 Chart displays the yield of crude luteins which are extracted from natural material directly by supercritical fluid at 60° C., pressure 300, 350 and 400 bar.

FIG. 2 Chromatogram of crude lutein obtained in FIG. 1 showing the small amount of free lutein and high amount of lutein ester.

FIG. 3 Chart displays the yield of crude lutein extracted (from natural material after modification of lutein ester in marigold) by supercritical fluid at temperature and pressures according to this invention.

FIG. 4 Chromatogram of crude lutein in obtained in FIG. 3 showing the high, amount of free lutein which is also highly purified.

DETAILED DESCRIPTION

In this invention, “crude lutein” means crude product which contains lutein as finished product.

When the method according to this invention is applied to total xanthophylls/other beside lutein, “crude lutein” means crude product of xanthophylls/other beside lutein. Therefore, the words “lutein” and “xanthophylls” are interchangeable throughout the invention.

Detail of the extraction method of lutein from natural materials according to this invention is described below.

Method for extracting natural lutein comprises of:

-   -   a. Pretreatment of natural materials containing lutein by         modification of natural lutein ester in the natural materials to         free lutein and/or low molecular weight lutein ester which         facilitate the extraction process.     -   b. Extraction wherein comprises of contacting the said         pretreated natural materials in (a) with supercritical fluid,         adjusting temperature and/or pressure by selecting the optimal         condition between 30-100° C., 200-450 bar for a certain period         of time to allow the maximum solubility of free lutein and/or         low molecular weight lutein ester in the super critical fluid.     -   c. Separation of solid materials from the fluid, after         extraction, and adjusting temperature and/or pressure to         minimize the solubility of extracted materials in the fluid and         collecting of the said extracted materials which is the crude         lutein.

According to the said method, the said natural materials can be selected from marigold flower, kale, spinach, algae, microbial cells including bacteria, yeasts, fungi and microalgae.

According to the said method, the said natural materials is hydrolyzed with low molecular weight acid and followed by removing of the said acid by washing with water and/or drying and/or grinding before subjecting the said materials to step (a). The acids can be organic acids i.e. acetic acid or inorganic acids i.e. hydrochloric acid, etc.

The modification of lutein ester in step (a) is saponification which is widely used. For example, the said saponification can be done by using KOH and ethanol at the optimal temperature and time depending on the natural material used. The modification of lutein ester may be achieved by esterification with low molecular weight acid i.e. hydrochloric acid and ethanol or transesterification using KOH and methanol.

The fluid according to this invention can be selected from carbon dioxide, ethanol or combination thereof. However, carbon dioxide is preferable.

In some cases, depending on the natural material used as raw material, co-solvent such as non-toxic natural oil i.e. palm oil, soybean oil, olive oil or combination thereof can be used together with the fluid in order to improve the extraction efficiency.

In step (b), extraction with fluid, the optimal condition is between 40-70° C., 300-400 bar. This condition yields maximum crude lutein because of the “not too high” temperature and to pressure when compared to the existing methods.

Moreover, the method for extraction may further comprises of step (d) purification of crude lutein by chromatography.

This invention also relates to crude product of lutein obtained from the extraction method previously described and the purified lutein obtained from chromatography.

It is important to note that this invention does not use solvent which may cause the (partial) degradation during the solvent removal. This invention employs the modification of lutein ester in natural materials directly. This has advantage in no waste of lutein before the extraction with fluid. Meanwhile, the extraction should also provide the smooth and more effective flow due to the molecular weight of extracting target compounds due to the reduced weight of the molecular weight.

Below is the examples with reference to drawings but it is not meant to limit the scope of invention by these examples.

EXAMPLES Hydrolysis

Fresh petals of marigold were hydrolyzed with low molecular weight i.e. acetic acid or hydrochloric acid in order to break down celluloses for 30 minutes. The hydrolyzed petals were washed with water and then dried or sun-dried and grinded to form powder.

Modification (modification of lutein ester in natural materials to free lutein or lutein esters with low molecular weight)

One gram of hydrolyzed powder of marigold was added with 2 ml of 95% ethanol at the temperature of 75° C. Then 2 ml of 40% alkaline solution was added and incubated at 75 c for 4 hours. The solution was cooled to 65 c and pH was adjusted to 7 using 25% hydrochloric acid in order to terminate the saponification. The solution was then dried.

Extraction With Super Critical Carbon Dioxide

In this step, super critical carbon dioxide extractor 10 ml. (model SFX-220, ISCO) was used. Saponified marigold powder (1 g) was added to the said extractor before allowing the super critical carbon dioxide to contact with the said powder. Select temperature and/or pressure to optimal condition between 40-120 c, 200-500 bar for 4 hours or other duration in order to maximize the solubility of free lutein and/or lutein ester with low molecular weight in super critical carbon dioxide. The optimal condition should be between 35-45 c and 300-400 bar. The system allows the recycling of carbon dioxide or optionally the release of carbon dioxide to atmosphere.

The applicant performed experiments by selecting the following conditions;

-   -   1) Temperature 40° C., pressure 150, 200, 250, 300, 350 and 370         bar     -   2) Temperature 60° C., pressure 150, 200, 250, 300 and 325 bar     -   3) Temperature 80° C., pressure 150, 200, 250 and 290 bar     -   4) Temperature 100° C., pressure 150, 200, 250 and 275 bar     -   5) Temperature 120° C., pressure 150, 200 and 255 bar

The results of crude lutein products obtained from above experiments were shown in graph FIG. 3. From FIG. 3 it can be seen that at the temperature of 40° C. and pressure 375 bar, crude lutein is 98.5% and at the temperature of 60° C. and pressure 330 bar, the crude lutein is also 98.5%.

In conclusion, if low temperature was used, the higher pressure must be required in order to maximize the yield of lutein. In contrast, if higher temperature was used, the lower pressure can then be applied. However, too high temperature and lack of oxidation protecting agent will cause the degradation or decomposition of lutein at the unacceptable level.

When compare the method according to this invention in FIG. 3 and the method in FIG. 1, it shows that at the temperature of 60° C., the method according to this invention only require the pressure at 375 bar and yield the crude lutein up to 98.5% whereas the pressure of the method in FIG. 1 must be at 400 bar and the yield of crude lutein is only 74.40%. It can be concluded that the method according to this invention is more efficient.

The experiment also indicated by the above mentioned graph that the extraction can be done at the temperature as low as 30° C.

Separation Of Debris And Collecting Of Crude Lutein

After extraction was completed, the debris was separated. The remaining solution was adjusted to the temperature and/or pressure which allow the minimum solubility of the extracted material in carbon dioxide. The carbon dioxide was then evaporated and the crude extract which was lutien was collected in the glass tube wrapped with aluminum foil and stored in the dark at 4° C.

Purification

Purification of free xanthophylls obtained from free xanthophyll ester and fatty acid was performed in normal phase chromatography using 35mm×240 mm silica column (100 g silica). Mobile phase comprises of 70:30 hexane:ethyl acetate was pumped to the column at the flow rate of 5-10 ml/min by a peristaltic pump. The samples were collected at every 10 minute. At the flow rate of 10 ml/min, xanthophylls with the purity of 99.5% will be obtained with the yield of 46% as shown in FIG. 4.

FIG. 4 shows the chromatogram of crude lutein as present in FIG. 3 which indicated that the amount of lutein in crude lutein product is higher than those obtained from the method according to FIG. 1. FIG. 4 also showed that crude lutein product is almost pure lutein (100%) whereas the crude lutein product obtained by the method according to FIG. 1 contained a lot of lutein ester as shown in the chromatogram in FIG. 2.

Although the marigold was used in this example as a sample of natural materials, the method according to this invention can also be applied to other natural materials containing lutein i.e. kale, spinach, microbial cells including bacteria, yeasts, fungi and microalgae and algae.

However, person skilled in the art can also modify this invention and the said modification is also considered to be within the scope of this invention. Person skilled in the art also understand that the principle of the extraction method according to this invention can be applied to xanthophylls extraction (with or without lutein) from the natural materials containing xanthophylls by adjusting the condition to be suitable for the said natural materials and selected xanthophylls.

BEST MODE

As described in the detailed description. 

1. Method of extracting lutein from natural materials, the method comprising: a. Pretreatment of natural materials containing lutein by modification of natural lutein ester in the natural materials to free lutein and/or low molecular weight lutein ester, which facilitate the extraction process; b. Extraction comprising contacting the pretreated natural materials in (a) with a supercritical fluid, adjusting temperature and/or pressure by selecting optimal conditions between 30-100 C, 200-450 bar for a certain period of time to allow maximum solubility of the free lutein and/or the low molecular weight lutein ester in the supercritical fluid; c. Separation of solid materials from the supercritical fluid, after extraction, adjusting temperature and/or pressure to minimize solubility of extracted materials in the supercritical fluid, and collecting of the extracted materials wherein the extracted materials comprise crude lutein.
 2. Method according to claim 1 wherein the natural materials are selected from marigold flower, kale, spinach, algae, microbial cells including bacteria, yeasts, fungi and microalgae or a combination thereof.
 3. Method according claim 1 or 2 wherein the natural materials are hydrolyzed with low molecular weight acid and followed by removing of the acid by washing with water and/or drying and/or grinding before subjecting the natural materials to step (a).
 4. Method according to claim 1 or 2 wherein the modification of the lutein ester in step (a) comprises saponification.
 5. Method according to claim 1 or 2 wherein the modification of the lutein ester in step (a) comprises esterification.
 6. Method according claim 1 or 2 wherein the modification of the lutein ester in step (a) comprises trans-esterification.
 7. Method according to claim 1 wherein the supercritical fluid is selected from carbon dioxide, ethanol or a combination thereof.
 8. Method according to claim 7 wherein the preferable supercritical fluid is carbon dioxide.
 9. Method according to any claim of claims 1, 2, 7, or 8 wherein the method further comprises using co-solvents with the supercritical fluid, wherein the co-solvents are selected from non-toxic natural oils, i.e. palm oil, soybean oil, olive oil or a combination thereof.
 10. Method according to any claim of claims 1, 2, 7, or 8 wherein the optimal conditions include temperature between 40-70° C., and pressure between 300-400 bar.
 11. Method according to claim 1 wherein the method further comprises purification of the crude lutein by chromatography.
 12. Crude lutein obtained from the method according to claim
 1. 13. Pure lutein obtained from the method according to claim
 11. 14. Method according to claim 1 wherein the method is used for extraction of total xanthophylls/or others beside besides lutein.
 15. Total xanthophylls/others besides lutein obtained from the method according to claim
 14. 